WO1997028459A1 - Vehicle with millimeter-wave radar - Google Patents

Abstract

A vehicle with a millimeter-wave radar capable of accurately detecting a stationary object around the vehicle while positively accepting ground clatters. Accordingly, the vehicle is provided with a millimeter-wave transmitting/receiving antenna (2F) fixed thereto with the center (C) of an antenna beam directed to a road surface (5), and a discrimination element (6) for classifying detected objects (4) by discriminating between objects (4a) the distance (L) to which varies with a movement of the vehicle and objects (4b) the distance (L) to which does not vary with a movement of the vehicle.

Description

 Technical Specification Vehicles equipped with millimeter wave radar

 In particular, the present invention relates to a vehicle equipped with a millimeter-wave radar that detects a stationary object around the vehicle while actively receiving ground clutter. Background technology

 Recently, attempts have been made to equip high-speed vehicles with millimeter-wave radars to prevent accidents due to inattentiveness and misjudgment of drivers on highways. Millimeter wave radars have shorter wavelengths than microwave radars, so the transmitting and receiving antennas can be made smaller (easy to mount on the vehicle), and the antenna beam width can be narrower (clutter from environmental objects is less likely). In addition, attention has been paid to advantages such as that a relative speed with respect to a detection object based on the Doppler frequency can be detected with high accuracy.

 As shown in FIG. 4, a conventional vehicle 1 equipped with a millimeter wave radar is provided with a millimeter wave transmitting / receiving antenna 2 at a height h of about 0.7 m from the ground in front of the vehicle 1. The millimeter wave transmitting / receiving antenna 2 has an antenna beam center C in a horizontal or upward state (8≥0 °, where 3 is shown) so as not to be affected by road surface reflection (hereinafter referred to as ground clutter G). And the antenna beam width 0 is narrow. Then, the transmitting antenna 3a emits the transmitting wave 3a forward, and the receiving antenna 2b receives, for example, the reflected wave 3b from the traveling vehicle at a distance of 100 m, and the distance between the vehicle 1 and the preceding vehicle. L and relative speed V can be detected. A pulse method, a two-frequency CW method, an F1V [—CW method, and the like are known as processing for the transmitted wave 3a and the reflected wave 3b in the millimeter-wave radar. Frequency analysis methods such as lutabank and FFT (Fast Fourier Transform) are used.

Conventional Millimeter-wave radar-equipped vehicle 1, as described above, It is important to not be affected. However, construction vehicles such as dump trucks and wheel loaders that travel at construction sites, mines, quarries, etc.

Rather, it is desirable to accurately detect a stationary object while actively receiving the ground clutter G.

 (1) For example, to detect the presence of a steep descent (corresponding to a stationary object), "Forward detection J. To detect hoppers and cliff edges (corresponding to stationary objects), there is “backward detection”.

 (2) The travel paths of construction sites, mines, quarries, etc. are usually fixed courses. In such courses, research on fleet operation with multiple unmanned vehicles is active. In unmanned fleet entrainment, each vehicle stores course data obtained by teaching in advance, or each vehicle is given the course data from outside through various communication means. However, since the above road is an undeveloped road surface, the slip ratio of wheels and crawlers, for example, varies greatly depending on the weather (rain, snow) and soil quality. For this reason, even if the rotational speed of the wheels and the like are detected and the travel distance and the vehicle speed V of the vehicle or the distance L between the vehicle and a specific object (for example, a straight line, a curve, a preceding vehicle, an intersection, etc.) are obtained, The value will be incorrect. Therefore, it is impossible to achieve fleet operation only with the course data. That is, in the case of an unmanned vehicle, in addition to the above “forward detection” and “backward detection J”, for example, the edge of a cliff to prevent the vehicle from falling down to the bottom of a curve, equipment, etc. (a stationary object) is detected. “Side detection” is also required. Disclosure of the invention

 The present invention has been made in view of the above circumstances, and has as its object to provide a vehicle equipped with a millimeter-wave radar that accurately detects a stationary object around the vehicle while actively receiving ground clutter.

 The vehicle equipped with the millimeter wave radar according to the present invention is:

The vehicle is equipped with a millimeter wave transmitting and receiving antenna, which emits a transmitting wave from the transmitting antenna to the surroundings, In a vehicle equipped with a millimeter wave radar that receives reflected waves from surrounding objects with a receiving antenna and can detect at least the distance between the vehicle and the object,

The millimeter wave transmitting / receiving antenna is installed with the antenna beam center facing the road surface.

It is characterized by comprising a discriminating unit for dividing a detected object into an object whose distance changes as the vehicle moves and an object whose distance does not change.

 According to this configuration, first, an object that does not change is detected as a road surface, that is, a ground crash. If an object having a higher reflection intensity than ground clutter exists on this road surface, this object is detected as an object whose distance changes, separated from the road surface.

 A storage unit for storing course data of the vehicle in advance;

The information processing apparatus may further include a first specifying unit that inputs information on the object whose distance changes from the discrimination unit, checks the input information against the course data, and specifies the object whose distance changes as the first specific object.

 According to such a configuration, the “changing object” detected and distinguished from the road surface is identified as an object that is useful in the course data, for example, a downhill or a cliff. Therefore, the operator or the unmanned vehicle can take an appropriate response manually or automatically based on the specified information.

 Further, an extraction unit may be provided which inputs information of an object whose distance does not change from the discrimination unit and, when this information changes, extracts a changing object based on the changed information. According to this configuration, when the road surface (that is, the ground clutter) that has been detected as an unchanging object changes, it is possible to recognize, for example, a downhill or a cliff, based on the changed information. Therefore, the operator can manually deal with the information (changed object) from the extraction unit.

 A storage unit for storing course data of the vehicle in advance;

The information of the changing object input from the extraction unit is compared with the course data, and the changing object is

And a second specifying unit that specifies the specified object. According to this configuration, not only the extracting unit but also the second specifying unit that specifies the changing object is provided. Therefore, the changing object is compared with the course data, and the changing object is, for example, a downhill or a cliff. And specifically recognize. Therefore, the operator or the unmanned vehicle can perform an appropriate response according to the specific information manually or automatically. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is an explanatory diagram of a vehicle equipped with a millimeter-wave radar that collectively describes first to fifth examples according to the present invention,

FIG. 2 is a perspective view of a millimeter wave transmitting / receiving antenna according to the present invention,

FIG. 3 is an explanatory diagram of the data processing principle of the FM-CW system according to the present invention,

FIG. 4 is a perspective view of a vehicle equipped with a millimeter-wave radar according to the related art. BEST MODE FOR CARRYING OUT THE INVENTION

 Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

 As shown in Fig. 1, Vehicle 1 has four millimeter wave transmitting and receiving antennas 2F, 2B, 2L, and 2R mounted at a height of 1.5 to 3 m above and below the ground in front, back, left, and right. are doing. Here, the mounting position of each millimeter wave transmitting / receiving antenna is 2F on the front side of the vehicle 1, 2B on the rear side, 2L on the left side, and 2R on the right side.

As shown in FIG. 2, each of the millimeter wave transmitting / receiving antennas 2F, 2B, 2L, and 2R has a configuration in which a planar transmitting antenna 2a and a receiving antenna 2b are arranged adjacent to each other. The effective length D of the antenna is about 85 mm vertically and horizontally for both antennas 2a and 2b. The antenna beam center C (see Fig. 1) is mounted at a horizontal angle of less than 16 °. It should be noted that “−” of 1 ° J indicates that the vehicle 1 is downward with respect to the horizontal direction, and “−6 ° or less” indicates that the vehicle is downward with respect to the horizontal direction. ° or greater. Therefore, each receiving antenna 2 b receives reflected waves 3 b from the front, rear, left and right road surfaces 5 of the vehicle 1. That is, the road surface condition (that is, the ground crash G) is received by each receiving antenna 2b. The millimeter wave transmitting and receiving antenna 2F, When describing the entire 2B, 2L, and 2R, the specifications of the millimeter-wave radar attached to the vehicle 1 are described prior to the case description of the millimeter wave transmitting / receiving antenna 2. The Millimeter wave is an electromagnetic wave having a wavelength λ force of 1 to 10 mm (that is, 300 to 30 GHz). In this example, 15 mm (59.5 GHz) Under the CW method, frequency analysis is performed by FFT. As shown in Fig. 3, the FM-CW method modulates a millimeter wave (carrier) with a signal wave (a triangular wave in this example), mixes the transmitted wave 3a with the reflected wave 3b, and sets the beat frequency. ί bl and f b2 have been obtained. After that, the distance L and the relative velocity V between the vehicle 1 and the object 4 can be calculated by the following general formulas (1) and (2).

 L = C ・ (f b2 + f bl) / (8 Δ F ・ f m) (1)

 V = C ・ (f b2 − f bl) / 4 f o (2)

 Here, C is the speed of light, f bl is the “beat frequency on the increasing side” shown in FIG. 3, f b2 is the “beat frequency on the decreasing side” shown in FIG. 3, and is the frequency deviation width (75 in this example). MHz) and fm are the frequencies of the triangular wave (781.25 kHz in this example), and fo is the center frequency, which is the frequency of the millimeter wave (59.5 GHz).

By the way, FIG. 3 is an explanatory diagram in the case of a single object 4, but in order to detect a plurality of the objects 4, an FFT is employed in this example. That is, the reflected wave 3 b is the distance L to the object 4, the direction to the object (the deviation angle between the antenna beam center C viewed from the millimeter wave transmitting / receiving antenna 2 and the direction of the object 4), the effective reflection area of the object 4 The received intensity [dB] differs depending on,, etc. Therefore, the FFT focuses on the difference in the reception intensity [dB], sets a predetermined threshold value for the reception intensity [dB], and obtains a bead frequency of the reception intensity [dB] greater than the threshold value. By setting the ¾ value in this way, a plurality of reception intensities [dB] can be obtained. That is, when the object 4 is a single body, a pulse-like peak value is obtained, and when the object 4 is a continuum like the road surface 5, a continuous peak value over the entire antenna beam width β is obtained.The antenna beam width ø is Is represented by the following general formula (3). 0 is the antenna gain at the antenna beam center C where the antenna gain is the maximum. Is the half angle (1/2), indicating the effective spread range of the radio wave. In this example, it is 0 ^ 4 ° (that is, 2 ° each in the vertical and horizontal directions).

 θ ^ 70 · λ / Ό (3)

 Then, the distance resolution performance ΔL for the detected object in the radio radar is given by the following general formula (4). In this example, A L = 2 m (that is, ± l m before and after).

 Mm L = C / 2 mm F (4)

 In the example shown in FIG. 1, in a vehicle 1 equipped with a millimeter-wave radar having such specifications, a controller 100 such as a microcomputer is connected to the millimeter-wave radar. The controller 100

i) Among the plurality of detected objects 4, a discriminating unit 6, which separates into an object 4a whose distance L changes with the movement of the vehicle 1 and an object 4b which does not change,

ii) Storage unit 7, which stores course data A of vehicle 1 in advance,

iii) The first object which receives the information of the object 4a from the discriminator 6 and matches the object 4a with the course data A stored in the storage unit 7 to specify the object 4a as the specific object A1 (first specific object A1) Specific part 8,

iv) When the information of the object 4b is received from the discriminating unit 6, and when this information changes, the extracting unit 9 that extracts the changed object body 4b, and

 V) Receiving the information of the changing object Δ 4 b from the extracting unit 9, collating the changing object Δ 4 b with the course data A stored in the storage unit 7, and as a specific object A 2 (second specific object A 2) A second specifying unit 10 to be specified is provided.

If the vehicle 1 is a manned vehicle, the controller 100 is connected to an alarm device or a display device 200 provided in a driver's cab or the like. The display unit 2000 issues a warning to the driver or the like based on the input from the controller 100, and displays the presence or absence of the object 4, the distance, the relative speed, the specific object name, and the like. On the other hand, if the vehicle 1 is an unmanned vehicle, the controller 100 automatically controls the engine, governor, brake, steering, transmission, alarm, external communication, etc. of the unmanned vehicle 1. It is connected to a control unit 300 for controlling. The control unit 300 stores a predetermined program in advance, and stores a predetermined program and a controller. The automatic control is performed in response to an input from 100. As shown in FIG. 1, the vehicle 1 moves forward and backward on a road surface 5 between a rear cliff 51 and a forward slope 52, and a specific example will be described below.

 The first example will be described. Assume that vehicle 1 is moving forward. In the state shown in Fig. 1, the position of the millimeter-wave transmitting / receiving antenna 2 F of the vehicle 1 is F 0, the position forward by a distance LF 1 from the position F 0 is F 1, and further forward from the position F 1 by a distance LF 2 Let the position be F 2. Fig. 1 also shows the detection results of the millimeter wave transmitting / receiving antenna 2F at each position F0, F1, and F2, where the vertical axis represents the reception intensity [dB] and the horizontal axis represents the distance L. It is. When the entire transmitted wave 3a with the antenna beam width 0 hits the road surface 5, as shown in the detection results of the positions F 0 and F 1, even if the vehicle 1 moves, the ground clutter G is generated over the entire antenna beam width 0. Since the distance L 0 of the detected ground clutter G does not change, it is possible to detect that the ground clutter G is on the road surface 5. Therefore, the road surface 5 becomes the object 4b.

 At the position F2 where the vehicle 1 has advanced further, as shown in the detection result, the ground crash G disappears from around the start point of the downhill 52. In other words, the distance of the ground clutter G at the position F 2 changes “one A L” from L 0 to “L 0 — A L”. As a result, the change in the ground clutter G, which is the object 4b, is extracted, so that the existence of the downhill 52 can be recognized.

By the way, as shown in FIG. 1, when the object 4 exists within the antenna beam width 0, the reception intensity higher than the ground clutter G may be obtained from the object 4 depending on the conditions. However, as shown in the detection results at the positions F 0 and F 1, it is difficult to distinguish the object 4 from the ground clutter G when the object 4 does not carry the reflector M. Therefore, it is assumed that the object 4 in this example carries the reflecting mirror M. The reflecting mirror M gives the receiving antenna 2 b a reflected wave 3 b having a receiving intensity [dB] greater than that of the ground clutter G by setting the number of mirrors, the effective area, and the like. This is because the reception intensity [dB] of the ground clutter G is almost proportional to the horizontal angle ^ of the millimeter wave transmitting / receiving antenna 2F, but exceeds the reception intensity [dB] from the reflector M. Because there is no. As a result, when the vehicle 1 moves forward from the position F0 to the position F1, the distance L between the vehicle 1 and the reflector M changes as shown in the detection results of the positions F0 and F1, so that The presence of the object 4 carrying the reflector M can be confirmed. Therefore, the reflector M becomes the object 4a.

 Therefore, the reflecting mirror M is fixed near the starting point of the downhill 52. When the vehicle 1 further advances by the distance L F2, as shown in the detection result at the position F 2, the start point of the downhill 52 can be pinpointed by the reflector M. However, the distance detection accuracy (that is, the distance resolution performance) cannot be higher than ± 1 m. As described above, in the millimeter wave radar of this example, the antenna beam center C is less than 16 ° in horizontal angle, and the antenna beam width 0 is 1 with respect to the antenna beam center C. It is. This is because the Millimeter-wave radar of this example is not affected by the ground clutter G up to 4 ° downward. Therefore, even if the vehicle 1 approaches just before the starting point of the downhill 52, if the ground clutter G is present, the downhill 52 will be within the horizontal angle of the installation of the millimeter wave transmitting / receiving antenna 2F; You can also see that it is a downhill slope.

 A second example will be described. While the first example described above describes the detection of the downhill 52 in the forward direction, this example is an example of the detection of the cliff 51 when the vehicle 1 moves backward. In Fig. 1, the Millimeter wave transmitting / receiving antenna 2B on the rear surface of the vehicle 1 shows i) the position B0 in the state shown in Fig. 1; iii) The data detected at position B2, which is backward from position B1 by distance LB2, are also shown. In the detection data, similarly to the first example, the vertical axis represents the reception intensity [dB], and the horizontal axis represents the distance L. According to the second example, the presence of the cliff 51 corresponding to the object 4b and the presence of the reflector M (corresponding to the object 4a) provided near the edge of the cliff 51 are detected by the same detection as the first example. You can check.

A third example will be described. This example is an example in which detection is performed by the left and right millimeter wave transmitting and receiving antennas 2L and 2R shown in FIG. According to this example, the state of the shoulder such as the cliff 51 and the reflector M can be detected. From the above, if the vehicle 1 is provided with the discriminating unit 6 or the discriminating unit 6 and the extracting unit 9 in the discriminating unit 6 and the extracting unit 9 in FIG. 1, the first to third examples described above are appropriate. Can be achieved.

 A fourth example will be described. In order for the vehicle 1 to be used for fleet operation, the vehicle 1 needs to store course data A in the storage unit 7 in advance, for example. Further, the vehicle 1 includes a first specifying unit 8 that receives the information on the object 4a from the discrimination unit 6, compares the object 4a with the course data A in the storage unit 7, and specifies the object 4a. did. By this matching, the object 4a is specified as a specific object A1 such as a cliff 51, a downhill 52, a corner, an intersection, or the like.

 Specifically, the detectable reflector M (i.e., the object 4a) is not only used to check the starting point of the downhill 52 or the vicinity of the edge of the cliff 51, but also to check the curve, intersection, straight line, etc. It is also provided at the beginning, middle, and end. In addition, the meaning of each reflector M is stored in the course data A together with the installation position. As a result, the first specifying unit 8 compares the detected reflector M with the course A of the storage unit 7 and finds that the reflector M is a specific object A1, for example, “downhill”. The specific object A1 with this meaning is input to the control unit 300. The control unit 300 allows the vehicle 1 to operate in a free flight based on this input. If the vehicle 1 is a manned vehicle, the detection result (specific object A 1) by the first specifying unit 8 may be input to the display 200 or the like.

A fifth example will be described. As is clear from the first to third examples above, the presence or absence of the downhill 52 and the cliff 51 is determined by the extraction unit 9 of the changing object 4b even without the reflector M (that is, the object 4a). Presence or absence can be almost confirmed. That is, the information of the changing object Δ4b from the extracting unit 9 and the course data A stored in the storage unit 7 are collated in the same manner as in the fourth example, and the changing object Δ4b is, for example, “downhill” or It is identified as a specific object A2 called “cliff”. This specification is performed by the second specifying unit 10 shown in FIG. Then, the specified result, that is, the specified object A 2 is also input to the control unit 300 as in the fourth example. This also makes fleet operation of vehicle 1 possible. If the vehicle 1 is a manned vehicle, the specific result may be input to the display 200 or the like. As described above, FIG. 1 collectively illustrates the first to fifth examples. In order to obtain the operation and effect described in the above example without excess or deficiency, the vehicle 1 must include at least the discriminator 6 (first combination), the discriminator 6, the storage 7, and the first identifier 8 (second combination). It is only necessary to have one of the discriminator 6 and the extractor 9 (third combination), the discriminator 6, the storage 7, the extractor 9 and the second specifying unit 10 (fourth combination). Of course, it may have all. The present invention is a vehicle 1 equipped with a millimeter wave radar that accurately detects a stationary object around the vehicle 1 while actively receiving the ground clutter G.

 In each of the above cases, the transmitting antenna 2a and the receiving antenna 2b used a flat shape with an effective antenna length D of 85 mm in length and width, but when the detection width of the road surface 5 in the front-rear and left-right directions was to be increased (That is, when it is desired to increase the antenna beam width 0), the millimeter wave transmitting / receiving antenna 2 may be scanned back and forth and right and left. Alternatively, as is apparent from the general formula (3), the millimeter wave transmitting / receiving antenna 2 may be made smaller (that is, the effective antenna length D is made smaller) and the wavelength λ is made larger. Industrial applicability

 INDUSTRIAL APPLICABILITY The present invention is useful as a vehicle equipped with a millimeter wave radar that can accurately detect a stationary object around a vehicle while actively receiving ground clutter.

Claims

The scope of the claims 1. The vehicle (1) is equipped with a millimeter wave transmitting / receiving antenna (2), which transmits a transmitting wave (3a) from the transmitting antenna (2a) to the surroundings and receives a reflected wave (3b) from the surrounding object (4). A vehicle equipped with a millimeter wave radar that receives an antenna (2b) and detects at least a distance (L) between the vehicle (1) and the object (4). The millimeter wave transmitting / receiving antenna (2F) is installed with the antenna beam center (C) facing the road surface (5), The detected object (4) is divided into an object (4a) in which the distance (L) changes with the movement of the vehicle (1) and an object (4b) in which the distance (L) does not change. A vehicle equipped with a millimeter-wave radar, comprising a discriminator (6). 2. a storage unit (7) for storing in advance the course data (A) of the vehicle (1); The information of the object (4a) whose distance (L) changes is input from the discriminator (6), and the input information is compared with the course data (A) to change the distance (L). 2. The vehicle equipped with a millimeter wave radar according to claim 1, further comprising: a first specifying unit (8) for specifying the object (4a) as a first specific object (A1). 3. Information of the object (4b) whose distance (L) does not change is input from the discriminator (6), and when the information changes, a changing object (A4b) is extracted based on the changed information. 2. The vehicle equipped with a millimeter wave radar according to claim 1, further comprising an extraction unit (9). 4. a storage unit (7) for storing course data (A) of the vehicle (1) in advance; The information of the changing object (A 4b) input from the extracting unit (9) is collated with the course data (A), and the changing object (A 4 b) is specified as the second specific object (A2). The vehicle equipped with a millimeter wave radar according to claim 3, further comprising a second identification unit (10). Ζ ΐ 90r00 / .6dT / XDd [6S ^ 8Z //. 6 O